Excavate

:This article is about the protist group called excavates. For the process of digging, see excavation.

Related Topics:
Protist - Excavation

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The excavates are a major line of protists, including a variety of free-living and symbiotic forms. They are usually characterized by having two, four, or more flagella with distinct ultrastructure anterior to a ventral feeding groove supported by microtubules. However, various groups that lack these traits may be considered excavates based on genetic evidence. Most excavates fall into four groups, which may be treated as phyla:

Related Topics:
Protist - Flagella - Ultrastructure - Microtubule

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Of these, the Percolozoa and Euglenozoa appear to be particularly close relatives, and are united by the presence of discoid cristae within the mitochondria. The jakobids have tubular cristae, like most other protists, and the metamonads are unusual in having lost their mitochondria. Their relationships are still uncertain, and it is possible that they are not monophyletic groups.

Related Topics:
Crista - Mitochondria - Monophyletic

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The excavates are often considered among the most primitive eukaryotes, and may be paraphyletic to the others. However, this placement may be an artifact caused by long branch attraction, as has been seen with some other amitochondriate groups, and in some phylogenies the excavates show up as an advanced group.

Related Topics:
Eukaryote - Paraphyletic - Long branch attraction

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